1. Field of the Invention
This invention relates generally to a diagnostic recording and more specifically, it concerns such a recording that is readable by a computer system for enabling a user without special knowledge, software, or equipment to check, isolate and identify certain hardware malfunctions within the system.
2. Description of the Prior Art
When using a computer system and a failure to properly read a specific piece of data occurs, several questions are raised. One question is whether or not the signal-to-noise quality of the system is satisfactory. Another question is whether or not the read head is in proper alignment. To answer these questions, skilled service has been required. To determine disk drive alignment, current practice requires removal of the drive from the disk system by a skilled serviceman, who connects the drive to an exerciser, inserts an alignment disk, and with an oscilloscope interprets the pattern to determine if the drive alignment is satisfactory for the purpose intended. This requires several hours of down time for the system and the services of a skilled technician with proper equipment.
Disks for aligning disk drives with an oscilloscope are well known. A flexible magnetic disk with signals varying on either side of a track centerline is disclosed in U.S. Pat. No. 4,084,201 to Hack, et al. These signals are read and interpreted with the aid of an oscilloscope to check and make track adjustment, ascertain disk eccentricity and spindle eccentricity, check functioning of a magnetic head, and adjust the azimuth angle of the head. U.S. Pat. No. 3,593,331 to Connell, et al., discloses an alignment disk with a three-track arrangement that provides a group of signals which may be read with a plurality of read/write heads and interpreted with the aid of an oscilloscope to produce an electrical function representative of disk alignment.
Automatic control systems for maintaining alignment of transducers are disclosed in U.S. Pat. No. 4,068,267 to Inouye; U.S. Pat. No. 4,149,200 to Card; U.S. Pat. No. 4,157,576 to Hack; U.S. Pat. No. 4,190,859 to Kinjo; and U.S. Pat. No. 4,213,148 to Clemens. U.S. Pat. No. 4,223,187 to Yonezawa, et al., discloses obtaining an alignment signal by analyzing signal variations caused by known undulations in the recording track.
Attempts have been made to write a disk in machine-readable code in an off-track manner. These attempts were based on an assumption that if the drive in question could read a track offset in either direction from a correct track centerline position by one-half track width, the head alignment must be satisfactory. This assumption is erroneous. A signal degrades but 50 percent of the signal level for a one-half track width offset condition, and most disk drives will produce error-free signals well beyond this offset because the 50 percent signal level due to off-track conditions is basic to design in this type of device. Thus, such disks with off-track data will be read with failure points determined only by indeterminate system noise.